Composition for use in the testing of smoke detectors

ABSTRACT

A composition for use in testing smoke detectors, comprises a polyhydroxy alcohol and a surface-active agent.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of the filing date under 35USC §119 of prior U.K. patent application no. 0106627.3, filed Mar. 16,2001, the disclosure of which is incorporated herein by this reference.

BACKGROUND

[0002] This invention relates to a composition for use in the testing ofsmoke detectors. More particularly it relates to a composition for thetesting of both ionisation and optical smoke detectors. The inventionalso relates to the use of a composition for such a purpose.

[0003] Smoke detectors are a common means of safeguarding lives andproperty against fire and smoke damage, in both commercial and privatepremises. Smoke detectors respond to smoke particles or aerosolsresulting from combustion and sound an alarm in response to theirpresence in the atmosphere. A rapid and reliable response by suchdetectors is vital, due to the dangers of smoke inhalation, and thespeed of propagation of fires.

[0004] Smoke detectors currently operate by one of two methods, namelyionisation or photoelectric principles. The operation of ionisationsmoke detectors is based on the principle of change in conductivity ofthe atmosphere within the measurement chamber of the smoke detector. Thechamber contains two electrodes, which create an electric field acrossthe chamber, and a very small source of a radioactive material,typically 0.2 g of americium-241. The radioactive material ionises theair particles, creating positive and negative ions inside the chamber.The movement of these ions towards the oppositely charged electrodecauses an electrical current to flow within the chamber. The currentstrength depends on the number and velocity of the ions, and will remainrelatively constant in air. When large, highly ionised smoke particlesenter the measurement chamber, they are attracted to oppositely chargedions, creating ion-particle pairs of high mass. Ions in suchion-particle pairs are unable to move within the chamber as freely asisolated ions, and the reduction of the electrical current across thechamber triggers the alarm. Ionisation detectors are generally suited tosmoke aerosols from flaming fires whose diameters range from 0.01-0.05μm. They are also affected by the electrical properties of smoke, inparticular, the mobility of the ion-particle pairs formed within thechamber.

[0005] Photoelectric or optical smoke detectors detect the presence ofsmoke particles due to their light scattering effects within thechamber. In one design, the chamber of the optical smoke detectorcontains an infrared light and a photodiode. Within the chamber, pulsesof infrared light are emitted which, in the absence of smoke particles,do not reach the photodiode. In the presence of smoke, however, infraredlight is reflected by the particles onto the photodiode, whichsubsequently relays the signal to an alarm unit, triggering an alarm.Photoelectric detectors are most responsive to smoke aerosols fromsmouldering sources, which exhibit particle diameters in the range of0.1-5 μm. In addition to particle size, another important factor in theeffectiveness of photoelectric detectors is the refractive index of thesmoke particles. Refractive index dictates the amount of scattering,reflecting and absorbing of light radiation required to trigger thealarm.

[0006] Typically, smoke detectors are provided with an integral testmechanism, which may be actuated by depressing a button on the housingof the detector or a similar means. Such testing mechanisms, however,only test the alarm mechanism, and provide no information about thestatus of the test chamber and smoke detection means. Over time, theaccumulation of interferants such as dust, dirt, grease, condensationand so on, and the ageing of the device, will affect the sensitivity ofthe smoke detection means, whilst not necessarily having any effect onthe alarm mechanism. In ionisation detectors, the interferants willshield the radioactive source, disrupting ionic current within thechamber, whilst in photoelectric detectors a film of interferants willform over the infrared source and photodiode sensors, reducing thesensitivity of the device. Consequently the integral test mechanism isinsufficient to provide an accurate view of the status of the smokedetector.

[0007] Methods are known in the art of functionally testing a smokedetector, using specific chemical compositions and methods of delivery.For example, U.S. Pat. No. 3,729,979 discloses an apparatus forgenerating and metering combustion products, which burns combustiblematerial such as cigarettes or cigars, for the testing of smokedetectors, and to allow the optimum positioning of smoke detectors.Blowing smoke at detectors, however, is primitive, unpleasant and can bedangerous.

[0008] U.S. Pat. No. 3,693,401 discloses an apparatus for checking theoperation of smoke detectors, comprising a housing member adapted to beplaced over a smoke detector, an internal space for the generation of anaerosol therein, and a container, containing a liquefied carrier medium,such as a fully halogenated hydrocarbon, for exampledichlorotetrafluoroethane. The carrier medium has a boiling point of−20° C. to +20° C., which is sufficiently high to ensure that it remainsin aerosol form for long enough to actuate optical smoke detectors aswell as ionisation detectors, before it evaporates. U.S. Pat. No.4,301,674 discloses a hand-held pressurised container, to allow fordirect spraying of a composition, in the form of an aerosol, whichsimulates products of combustion. The composition is preferablyapproximately 70% hydrocarbon propellant, 5% isopropyl alcohol, and 25%dioctyl phthalate. WO 92100240 also describes the use of an aerosolspray formulation comprising a linear alkyl phthalate ester andpropellant, for testing smoke detectors. U.S. Pat. No. 4,715,985describes a composition for checking the functioning of fire detectioninstallations, comprising triflourotrichloroethane, nitrous oxide, ethylether, and an alkyl phthalate. Furthermore, the use of phthalates isdescribed in GB patent no. 1527003.

[0009] The use of HCFCs and CFCs is now banned, however, due to theiradverse environmental effects. Also the use of phthalates hasdisadvantages, in that they are highly toxic in a respirable form, andhave undesirable effects on plastics, particularly styrenes, which arecommonly used in household goods.

[0010] These problems have been partially overcome by a method disclosedin U.S. Pat. No. 5,076,966, which involves a method for checking thefunctioning of ionisation or optical smoke detectors comprising thesteps of introducing into the vicinity of the detector a polyhydroxyalcohol and a water-soluble alcohol having a boiling point of below 100°C. Such compositions are not very effective at activating ionisationdetectors unless the polyhydroxy alcohol is at a high concentration. Athigh concentrations, however, this method will lead to the deposition ofa residue in and around the smoke detector, which is unsightly and canlead to diminished sensitivity of the detector.

[0011] Furthermore, others have replaced phthalates with silicon-basedcompositions, such as phenyltrimethicone, (U.S. Pat. No. 5,785,891) andsiloxanes (GB 2305917) with some success, although a residue may stillremain after application. Silicones and siloxanes are also a possiblerespiratory hazard, thermal decomposition of some will produceformaldehyde, and their use limits the application of the smoke detectorcompositions. JP HI 0-079090 describes a composition for testing a smokedetector comprising an alcohol and an additive, such as a carbonate or apolyalkylene glycol.

[0012] GB 2283978 describes a composition comprising a siloxaneoxyalkane surfactant and a polyol, as the reaction products for a closedcell rigid foam. GB 2243780 describes a composition comprising asilicone surfactant and optionally an alkane diol, for use as asunscreen.

[0013] Smoke detector manufacturers have shown that, to some extent,improving the structural and response design of an ionisation chambercan reduce the tendency to false alarms caused by interferants, but suchdesign improvements may not have a significant effect during thefunctional testing of smoke detectors where test products are oftenapplied directly into the chamber through the vents.

[0014] It is accordingly an object of the present invention to provide acomposition applicable with an aerosol device, capable of triggeringboth optical and ionisation type smoke detectors, whilst avoiding theproblems associated with the prior art.

[0015] The present invention relates to a chemical composition, whichforms aerosol particles of similar size, and molecular ions of similarweight and ionisation energy, in comparison to smoke aerosols. Due tothe aerosol particle size, and the weight and ionisation energy of themolecular ions, the composition is able to trigger ionisation smokedetectors, whilst the aerosol also has the correct particle size andrefractive index to trigger optical detectors. The composition iscompatible with a wide range of plastics, as well as being inert to theuser and to the environment, and enables the detector to be testedfunctionally, without leaving untoward residues on detector surfaces orother surfaces near the area of application.

[0016] According to one aspect of the invention, there is provided acomposition for the activation of smoke detectors, which comprises apolyhydroxy alcohol and a surface-active agent.

[0017] The polyhydroxy alcohol is an efficient photoelectric detectoractivator, which is harmless to health and the environment and isnon-aggressive to materials. The polyhydroxy alcohol may be present inconcentrations of 0.05-10% w/w. In addition, the polyhydroxy alcoholpreferably has a refractive index of between 1.45 and 1.5. Preferablythe polyhydroxy alcohol is 1,2-ethanediol, 1,2-propanediol,1,3-propanediol or 1,2,3-propanetriol, or mixtures thereof. Thepresently preferred formulation consists of 1,2,3-propanetriol(glycerol), desirably in quantities of 0.3% wt/wt and whose refractiveindex is 1.4746.

[0018] Surface-active agents, generally known for their emulsificationcharacteristics, are used in the present invention for their ability to(1) impart to particles adequate electrical potential, and (2) adsorbquickly around dispersed particles, forming a non-adherent film whichprevents coalescence between particles, thus maintaining correctparticle sizes for longer. This makes them good activators of ionisationdetectors. In addition, they generally exhibit high refractive indices,which makes them good activators of photoelectric detectors. Accordingto the hydrophilic-lipophilic balance (HLB) system, surface-activeagents are assigned a numerical value to indicate the polarity of themolecules in an arbitrary range of 1-40. High HLB values represent highpolarity of the molecules. The surface-active agent may be selected fromthe anionic and non-ionic surfactant classes. The anionic class mayconsist of linear sodium alkyl

[0019] benzene sulphates, linear alkyl sulphates and linear alkyl ethoxysulphates. The non-ionic class may include the alkyl ethoxylates,ethoxylated alkyl phenols, fatty acid esters, long chain carboxylic acidesters and polymers of ethylene oxide, propylene oxide and alcohols ormixtures thereof. The surface-active agent may be present in aconcentration of between 0.05-10% wt/wt and may have an HLB value in therange of 140 with a refractive index between 1.45 and 1.5, and have goodpolarity characteristics. The presently preferred formulation consistsof a sorbitan monolaurate (see above), a sorbitan ester having moderatepolarity characteristics, an HLB of 8.6, refractive index of 1.4740 andpreferably present in quantities of 0.2% wt/wt. It is commonly used inthe pharmaceutical, food and cosmetic industries and is therefore safeto use.

[0020] Preferably, the acid moiety of the ester is a saturated longchain carboxylic acid, wherein the backbone of the carboxylic acidcomprises preferably 5 to 20 carbon atoms.

[0021] According to another aspect of the invention, a composition foruse in testing smoke detectors is provided, comprising a polyhydroxyalcohol and a surface-active agent, wherein the polyhydroxy alcohol andsurface-active agent each has a refractive index of 1.45-1.5.

[0022] According to another aspect of the invention, a composition foruse in testing smoke detectors is provided, comprising a polyhydroxyalcohol, a surface-active agent selected from the group consisting of:alkyl ethoxylates, ethoxylated alkyl phenols, fatty acid esters, longchain carboxylic acid esters, polymers of ethylene oxide, polymers ofpropylene oxide, polymers of alcohols or copolymers thereof, andmixtures thereof; or linear sodium alkyl benzene sulphates; linear alkylsulphates; linear alkyl ethoxy sulphates; and mixtures thereof.

[0023] The composition preferably includes a carrier medium. The carriermedium is preferably a low boiling point alcohol or mixture of alcohols;the boiling point is preferably below 100° C. Preferably the carriermedium is selected from methanol, ethanol, 1-propanol, 2-propanol, and2-methyl-2-propanol, or suitable combinations thereof. Most preferablythe carrier medium is ethanol or 2-propanol. In a preferred embodiment,the carrier medium comprises from 5% wt/wt up to 30% wt/wt of thecomposition.

[0024] The composition preferably includes a propellant, in order tomake it suitable for use as an aerosol. The composition may contain from10% wt/wt up to 90% wt/wt of the propellant. It is preferably ahydrocarbon propellant (such as isobutane, propane and butane), HFC134a, DME (dimethylether), or suitable combinations thereof.

[0025] According to another aspect of the invention, a composition foruse in testing smoke detectors is provided, comprising 0.05-10% wt/wtpolyhydroxy alcohol 0.05-10% w/wt surface active agent, 5-30% wt/wtcarrier and 10-90% propellant.

[0026] The composition according to the invention is capable ofactivating both ionisation and photoelectric smoke detectors, and cantherefore be used in the testing of such smoke detectors.

[0027] The composition according to the invention may be contained indispensing equipment, capable of releasing said composition through avalve and actuator orifice to create an aerosol of substantiallyconstant particle size, conducive to the activation of optical andionisation smoke detectors. The composition is preferably containedwithin the dispensing device within a pressure range of 6-12 bar(600-1200 kPa). The preferred dispensing equipment is No Climb's “SOLO”dispensing equipment, which is designed to contain the released aerosolswithin the immediate vicinity of the detector until the detector alarmhas activated. This feature not only prevents direct introduction of theaerosolised components into the chamber, which can cause fouling, butalso provides controlled test conditions for the detectors under test.By using a housing or cup membrane placed over the smoke detector,conditions can be kept constant, and escape of the aerosol is minimised.

[0028] When the surface-active agent and polyhydroxy alcohol are appliedwith an appropriate amount of the carrier medium, such as an alcohol,through optimum valve/actuator specifications, residual deposits arekept to a minimum.

[0029] According to another aspect of the invention, a composition foruse in testing smoke detectors is provided, comprising 0.05-10% wt/wtpolyhydroxy alcohol 0.05-10% wt/wt surface active agent, 10-30% wt/wtcarrier and 10-90% propellant.

[0030] According to another aspect of the invention, there is providedan aerosol device comprising a housing containing a composition asdescribed above, and means to dispense said composition from the housingin an aerosol form. The aerosol device may contain the compositionwithin the device at a preferred vapour pressure of approximately 6-12bar (600 kPa -1200 kPa). In a preferred embodiment, the dispensing meanscomprises a valve and an actuator orifice for dispensing aerosolparticles of sizes conducive to photoelectric and ionisation smokedetector response.

[0031] According to another aspect of the invention, a method of testinga smoke detector is provided, comprising contacting the smoke detectorwith a composition comprising a surface-active agent. Advantageously,the surface-active agent is used in combination with a polyhydroxyalcohol. The composition will usually be contacted with the smokedetector by spraying. The method may further comprise the step ofdetecting whether the smoke detector alarm has been activated by thestep of contacting the smoke detector with the composition. This stepmay involve, for example, assessing whether an audible alarm hassounded, whether a visible signal has been activated or measuring theanalogue value of the alarm sensor and assessing whether it exceeds thealarm mode trigger value. This step may also comprise assessing theamount of composition brought into contact with the smoke detector.Usually, the length of time the composition is in contact with the smokedetector, and the amount of the composition present in the smokedetector chamber will enable the tester to assess the sensitivity andfunctioning of the smoke detector. For example, an alarm that isactivated by a small amount of the composition (e.g. a short 1-10 secondspray application in the case of the composition being applied byaerosol), and within a few seconds (e.g. less than 30), will beindicative of a correctly functioning alarm. If a more prolongedcontacting/application step is necessary, or the alarm takes some time(e.g. over 30 seconds) to activate, this is indicative of a lowersensitivity or poorly functioning alarm.

[0032] According to another aspect of the invention, a method of testinga smoke detector is provided, comprising contacting the smoke detectorwith a composition comprising: a polyhydroxy alcohol and asurface-active agent, wherein the surface-active agent has a refractiveindex from 1.45 and 1.5.

[0033] According to another aspect of the invention, a method of testinga smoke detector is provided, comprising contacting the smoke detectorwith a composition comprising: a polyhydroxy alcohol and a surfaceactive agent, wherein the surface-active agent is a polar non-ionicsurfactant with an HLB of 1-10.

[0034] Various compositions, comprising polyhydroxy alcohol atconcentrations of 0.1% -10% wt/wt dissolved in an alcohol, such asisopropyl alcohol, were assessed for their effectiveness in activatingsmoke detectors and residues deposited. At all concentrations, suchcompositions were found to be efficient in the activation ofphotoelectric smoke detectors, but poor in the activation of ionisationdetectors, particularly at low wt/wt % values. At high concentrations ofpolyhydroxy alcohol, activation of ionisation detectors was moreeffective, however the presence of undesirable residues was morenoticeable.

[0035] Similarly, various compositions, comprising sorbitan ester atconcentrations of 0.1%-10% wt/wt dissolved in an alcohol, such asisopropyl alcohol, were assessed for their effectiveness. At allconcentrations, such compositions were found to be very effective in theactivation of photoelectric detectors, with lower concentrations beingmore conducive to fast detector recovery rates and low levels ofresidues. The ionisation detector response was more moderate, but stilleffective.

[0036] Combining the two activities at desired levels in an alcohol suchas isopropyl alcohol produced a more superior response in photoelectricand, in particular, in ionisation detectors. The most favourableresponses were produced when a dispenser was used to introduce thecomposition into the vicinity of the detector.

[0037] Various aerosol compositions consisting of glycerol at 0.2%,0.3%, 0.4%, 0.5% and 1% wt/wt dissolved in isopropanol respectively andpropelled by HFC 134a were prepared and tested using the ApolloDiscovery™ range (Apollo Fire Detectors Ltd) of ionisation andphotoelectric smoke detectors. These high-specification analogueaddressable fire detectors can operate in one of five response modes,which are related to their sensitivity. Mode 1 will provide a highersensitivity to fires than mode 5, i.e. a detector in mode 1 can be moreeasily activated than one in mode 5.

[0038] Tests revealed that with glycerol levels at 0.5% or 1% wt/wt,only ionisation detectors in mode 1 (the most sensitive response mode)could be successfully activated by the aerosol. Levels of glycerol atabove 1% wt/wt produced residual deposits on the detector surface.

[0039] For photoelectric detectors, all response modes were successfullyactivated in adequate time (loss than 30 seconds). This confirmedglycerol as an effective photoelectric detector activator. These resultswere substantiated by observing the differences in the level of activitywithin the chambers through graphical profile output, which showed thathigher levels of activity were reached in the optical detectors.

[0040] Similarly, equivalent levels of sorbitan monolaurate weredissolved in isopropanol and duly tested. All response modes in bothtypes of detector responded within 30 seconds. Again, levels above 1%wt/wt produced noticeable residual deposits on the detector surface.This confirmed sorbitan monolaurate as an effective ionisation andphotoelectric smoke detector activator.

[0041] The invention is further frustrated with reference to thefollowing figures.

[0042]FIG. 1 is a graph showing the analogue value produced by theapplication of the preferred formulation, hand-sprayed from 30 cm at anApollo Ion detector.

[0043]FIG. 2 is a graph showing the analogue value produced by theapplication of the preferred formulation, sprayed by dispenser at anApollo Ion Detector.

[0044]FIG. 3 is a graph showing the analogue value produced by theapplication of the preferred formulation, hand-sprayed from 30 cm at anApollo Optical detector.

[0045]FIG. 4 is a graph showing the analogue value produced by theapplication of the preferred formulation, sprayed by dispenser at anApollo Optical Detector.

[0046] Quantitative tests were carried out by measuring the analoguevalue of the detector over time. To test the effectiveness of thecompositions, the analogue value of the two types of detectors wasmeasured during application of the preferred formulation from a distanceof 30 cm. When smoke is introduced into a detector, the analogue valuerises to a maximum value of 127, before falling when clean air replacesthe smoke in the chamber, to the clean air value (CAV) of 23.

[0047]FIG. 1 shows that even when hand spraying, a reasonable responsewas achieved in the ionisation detector, at mode 1 or mode 3 detectorlevels. As shown in FIG. 2, however, activity peaks a lot higher in theionisation detector, and the response is more rapid, when a dispenser isused, rather than testing by hand. The alarm is triggered, even when theionisation detector is set to mode 5. Importantly, the recovery time(time taken for the detector to return to quiescent conditions) of thealarm is more rapid when the formulation is applied with a dispenser.

[0048]FIGS. 3 and 4 shows that the even more effective results areachieved in optical sensors, using the preferred composition. Whensprayed by hand, the analogue value reaches the maximum value, even withthe detector in mode 5. Similarly, when a dispenser is used, theanalogue value reaches its maximum, however, the detector recovery timeis considerably faster than when the composition is hand sprayed,particularly when the detector is in a more sensitive mode.

1. A composition for use in testing smoke detectors, comprising apolyhydroxy alcohol and a surface-active agent, wherein the polyhydroxyalcohol and surface-active agent each has a refractive index of1.45-1.5.
 2. A composition according to claim 1, wherein the polyhydroxyalcohol is selected from the group consisting of 1,2-ethanediol;1,2-propanediol; 1,3-propanediol; 1,2,3-propanetriol; and mixturesthereof.
 3. A composition according to claim 1, wherein the polyhydroxyalcohol is 1,2,3-propanetriol.
 4. A composition according to claim 1,wherein the surface-active agent is a polar, non-ionic surface-activeagent.
 5. A composition according to claim 1, wherein the surface-activeagent has an HLB of 1-10.
 6. A composition according to claim 1, whereinthe surface active agent is selected from the group consisting of alkylethoxylates; ethoxylated alkyl phenols; fatty acid esters; long chaincarboxylic acid esters; polymers of ethylene oxide, polymers ofpropylene oxide, polymers of alcohols or copolymers thereof; linearsodium alkyl benzene sulphates; linear alkyl sulphates; linear alkylethoxy sulphates; and mixtures thereof.
 7. A composition according toclaim 1, wherein the surface-active agent is a sorbitan ester.
 8. Acomposition according to claim 1, wherein the surface-active agent issorbitan monolaurate.
 9. A composition according to claim 1, furthercomprising a carrier medium.
 10. A composition according to claim 1,further comprising a propellant.
 11. A composition for use in testingsmoke detectors, comprising 0.05-10% wt/wt polyhydroxy alcohol 0.05-10%wt/wt surface active agent, 5-30% wt/wt carrier and 10-90% propellant.12. A composition for use in testing smoke detectors, comprising apolyhydroxy alcohol, a surface-active agent selected from the groupconsisting of: alkyl ethoxylates, ethoxylated alkyl phenols, fatty acidesters, long chain carboxylic acid esters, polymers of ethylene oxide,polymers of propylene oxide, polymers of alcohols or copolymers thereof,and mixtures thereof; or linear sodium alkyl benzene sulphates; linearalkyl sulphates; linear alkyl ethoxy sulphates; and mixtures thereof.13. A method of testing a smoke detector, comprising contacting thesmoke detector with a composition comprising a polyhydroxy alcohol and asurface-active agent, and assessing the response of the smoke detector.14. A method according to claim 13, wherein the surface-active agent isselected from the group consisting of alkyl ethoxylates; ethoxylatedalkyl phenols; fatty acid esters; long chain carboxylic acid esters;polymers of ethylene oxide, polymers of propylene oxide, polymers ofalcohols or copolymers thereof; linear sodium alkyl benzene sulphates;linear alkyl sulphates; linear alkyl ethoxy sulphates and mixturesthereof.
 15. A method according to claim 13, wherein the surface-activeagent is a sorbitan ester.
 16. A method according to claim 13, whereinthe composition further comprises a carrier medium and a propellant. 17.A method according to claim 13, in which the composition is contactedwith the smoke detector by spraying.
 18. An aerosol device comprising ahousing containing a composition according to claim 1, and means todispense the composition from the housing in an aerosol form.
 19. Anaerosol device according to claim 18, wherein the vapour pressure of thecomposition contained within the device is approximately 6-12 bar(600-1200 kPa).
 20. An aerosol device according to claim 18, wherein thehousing comprises a valve and actuator orifice for dispensing aerosolparticles of sizes conducive to optical and ionisation smoke detectorresponse.